MissMissey is right. Ask 40 bakers and you'll get 20 answers.
For me, a
1/4 sheet is a 7x11 (1 mix) 12-18 servings
1/3 sheet is a 9x13 (1.5 mix) 20-26 servings
1/2 sheet is a 10x15 (2 mix) 25-35 servings
2/3 sheet is 12x18 (3 mix) 36-45 servings
Full is 20x15 (4 mix) 46-55 servings
I purchased my cake boards first, and then used the pans that went best with them. My 1/2 sheet cake board is 14x18, so the 12x18" pan would have touched the ends before it was even frosted... it's very confusing at times, because the supplier I use, actually sells different sizes with the same description! They sell 12x16, AND 12x18 for 1/2 sheets.... 8x12, AND 9x13 for 1/4 sheets, etc... I thought that was totally weird! So, I purchased my boxes, boards, and then pans....... THEN, I advise my customers of how many servings MY cakes will supply. I think everyone agrees that a sheet cake slice is 2x2" square (although I think some cut 2x1.5" squares actually)... so, my 12x16" half-sheet cake will serve 48. The customer gets to choose if they want to pay my price for that many servings (and they always do, I think I need to raise my prices! But that's another topic!) Good luck!
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